Regulation of intestinal homeostasis and epithelial barrier by LPA

描述(由申请人提供)： 项目概述炎症性肠病(IBD)，包括克罗恩病和溃疡性结肠炎，在美国有100多万人受到影响。IBD是一种常见的病因 美国退伍军人的住院情况。IBD增加了其他疾病的风险因素，如结直肠癌和动脉粥样硬化。肠道极化上皮作为入侵病原体和宿主免疫系统之间的屏障，在炎症中发挥着重要作用。对上皮的破坏影响了营养物质和矿物质的吸收，通常会导致IBD患者营养不良。因此，维持上皮屏障完整性的能力对于保护宿主免受肠腔内有害环境的伤害至关重要。肠上皮的增殖和迁移是伤口愈合的必要条件，而IBD则破坏了这一过程。溶血磷脂酸(LPA)是一种具有多种生长因子样作用的脂质介质。胞外LPA是由一种称为自体趋化蛋白(ATX)的溶血磷脂酶D降解循环中的溶血磷脂而产生的。LPA的作用是通过一族G蛋白偶联受体介导的：LPA1R-LPA5R。LPA1R是小肠和结肠中含量最丰富的LPA受体，但其功能意义尚不清楚。这一应用的动力来自我们最近的发现，即肠道中LPA1R的丢失通过延迟恢复过程而增加了对葡聚糖硫酸钠(DSS)诱导的结肠炎的易感性。我们的目标是进一步确定LPA1R在慢性炎症中的重要性，并确定LPA1R如何调节肠上皮细胞的动态平衡(目标1)。LPA通常被认为是一种促炎剂。我们发现，在DSS诱导的结肠炎中，产生LPA的ATX的表达水平增加，ATX表达缺陷的小鼠对DSS诱导的结肠炎表现出抵抗。然而，ATX的缺失或ATX的化学抑制显著延缓了DSS诱导的损伤的恢复。因此，LPA在炎症的发生和恢复过程中似乎有相反的作用。我们建议调查ATX是否是治疗肠道炎症的潜在靶点。我们将使用ATX的基因缺失和化学抑制来评估其对急性和慢性炎症的影响(目标2)。IBD患者，特别是克罗恩病患者，由于营养吸收减少和/或大量营养素损失增加，面临各种营养缺乏的风险。LPA1R的缺失或抑制降低了几种营养和电解质转运蛋白的表达。相反，用LPA治疗自发性回肠炎的小鼠增加了转运蛋白的表达，这表明LPA对肠道吸收功能有有益的作用。我们建议评估LPA是否可以用于增强与IBD相关的上皮吸收功能(目标3)。这项应用的首要目标是研究LPA在维持肠上皮细胞动态平衡以及调节上皮屏障和吸收功能方面的重要性。这项拟议工作的成功完成将有助于更好地了解LPA1R介导的作用，与拟议的关于主要产生LPA的ATX的研究将有助于维持健康的肠道，并为炎症性疾病的治疗提供潜在的治疗模式。

DESCRIPTION (provided by applicant): PROJECT SUMMARY Inflammatory bowel diseases (IBD), including Crohn's disease and ulcerative colitis, affect more than 1 million people in the United States. IBD is a frequent cause of hospitalization among US military veterans. IBD increases the risk factor for other diseases such as colorectal cancer and atherosclerosis. Polarized epithelia in the intestine play an important role in inflammation by serving as a barrier between an invading pathogen and the immune system of the host. Damage to the epithelia compromises absorption of nutrients and mineral, often leading to malnutrition in patients with IBD. Hence, the ability to maintain the epithelial barrier integrity is critical in protecting the host from a hostile environment in the intestinal lumen. Intestinal epithelial proliferation and migration are requirements in wound healing, a process disrupted in IBD. Lysophosphatidic acid (LPA) is a lipid mediator with diverse growth factor-like effects. Extracellular LPA is produced by hydrolysis of circulating lysophospholipid by a lysophospholipase D known as autotaxin (ATX). The effects of LPA are mediated through a family of G protein- coupled receptors: LPA1R-LPA5R. LPA1R is the most abundant LPA receptor in the small intestine and colon, and yet the functional significance of LPA1R is poorly understood. The impetus of this application came from our recent findings that loss of LPA1R in the intestine results increased susceptibility to dextran sulfate sodium (DSS)- induced colitis by delaying the recovery process. We aim to further define the importance of LPA1R in chronic inflammation and determine how LPA1R regulates intestinal epithelial homeostasis (Aim 1). LPA is often regarded as a pro-inflammatory agent. We found that the expression level of LPA-producing ATX was increased in DSS- mediated colitis, and mice deficient in ATX expression showed resistance to DSS-induced colitis. However, deletion of ATX or chemical inhibition of ATX significantly delayed recovery from DSS-induced injury. Hence, LPA appear to have opposing effects during the onset of inflammation and recovery. We propose to investigate whether ATX is a potential target in treatment of intestinal inflammation. We will use genetic deletion and chemical inhibition of ATX to assess the effects on acute and chronic inflammation (Aim 2). Individuals with IBD and, particularly, those with Crohn's disease are at risk for a variety of nutritional deficiencies because of decreased nutrient absorption and/or increased losses of macronutrients. Deletion or inhibition of LPA1R decreased expression of several transporters of nutrients and electrolytes. On the contrary, treating mice with spontaneous ileitis with LPA increased transporter expression, suggesting a beneficial role of LPA on the intestinal absorptive function. We propose evaluate whether LPA could be used to enhance epithelial absorptive functions associated with IBD (Aim 3). The overarching goal of this application is to investigate the importance of LPA in maintenance of intestinal epithelial homeostasis and regulation of the epithelial barrier and absorptive functions. Successful completion of the proposed work should provide a better understanding of the LPA1R- mediated effects, which together with the proposed study on the major LPA-producing ATX, will benefit maintenance of healthy intestine and provide potential therapeutic modality for treatment of inflammatory diseases.